Safety-switch.



H. W. CHENEY.

SAFETY `SWITCH.

APPLIoATIoN FILED JUNE 6, 1910.

v Patented Oct. 6, 1914.

'11. W. CHENEY.

SAFETY SWITCH. l APPLICATION FILED JUNI'. e, 1910.

Patented Oct. 6, 1914.

Y 2 SHEETS-SHEET 2.

UNITEDl STATES PATENT CEEICE.

HERBERT W. CHENEY, or MILWAUKEE, WIsCoNsIN, AssI'GNoR, BY MEsNE ASSIGN- MENTS, To 4ALLIs-CHALMERS MANUFACTURING COMPANY, A CORPORATION 0E DELAWARE. g

SAFETY-SWITCH.

Specication of Letters Patent.

Patented oet. e, 1914.

Application filed June 6, 1910. Serial N0. 565,302.

` a citizen of the United States, residing at Milwaukee, in the county of Milwaukee and State of Visconsin, have invented certain new and useful Improvements in Safety- Switches, of which the following is a full, clear, and exact specification.

This invention relates to a new and use-v ful safety switch to be used for controlling vthe operation of hoists and other similar mechanisms.

I-n operating hoists, cranes, and elevators there is danger of le'aving on the power after certain predetermined stopping points have been reached.'thus Causing damage, if not total destruction of the operating parts.

In view of the above it is the object of this invention to provide means for automatically breaking the power circuit and stopping the operation o the mechanism at certain predeterminedpoints to prevent accident.

By making the mechanism automatically controllable, it is not necessary to depend upon the operator, and accident from the carelessness of the operator or loss of control of thev mechanism is avoided.

For the purpose of illustrating and describing my invention, I have shown it arranged to prevent an overwind and also too great a lowering of the load on an electric l hoist.

As here shown, I have illustrated means whereby., when the safety switch has been opened, furtherelevation of the load is impossible when the upper safety limit hasv been reached; also further lowering of the load Yis impossible when the lower safety limit has been reached. The switch is arranged to'act as an absolute cutout so that when operated, the load may he neither be operated in the usual manner and means whereby after the switch is unlocked the `movable member of the switch is thrown forcibly with a' snap action out of engagement with the stationary member of the switch thus overcoming any vslight fusing between the contacts.

The various novel features of "the invention will be described in the specification l tion of the load at all times.

and-particularly set forth in the appended claims.'

In the accompanying sheets of drawings, Figure 1 is a front elevation, parts being removed, of an indicator and `its operating parts equipped with my invention, the latter not being shown in this view. Fig. 2 is a partial longitudinal sectional view of the upper part of the indicator apparatus showing the arrangement of the switch and 'switch mechanism; Fig. 3 is a partial'sectional view taken along the line 3-3 of Fig. 1 showingk means for resetting the switch after it has been opened; Figs. 4 and 5 are partialsectional views of the switch mechanism taken along the line 4 4 of Fig. 2 with the switch in its closed and opened positions respectively, and Figs. 6 and 7 are partial sectional views of the switch mechanism taken along the line 6-6 of Fig. 2 with the switch in closed and opened positions respectively.

In the operation of hoists it is desirable to provide the operating mechanism with some sort of indicator which shows the exact posiy Such an indi-r cator is shown in Fig. 1 with an indicator column 10 inclosing a threaded shaft 11 to which motion istransmitted from the hoist through meshing miter gears 12 and 13. These miter gears are inclosed in a housing' 111 which forms a support upon which the column 10 is secured. One of the gears 13 ismounted upon a shaft 15 which rotates in bearings 16 of thel housing 14, and mounted on the shaft 15 outside of the gear housing 14 is a sprocket wheel 17 y which is adaptV ed to coperate with a connecting chain which passes over a similar sprocket wheel on the drum shaft of hoists.

Engaging the threaded portion 18' of the shaft 11 is an indicator. 19 which travels 'the length of the shaft 11 and indicates the exact position of load at every instant. Secured to the outside of the indicator column is a rocker shaft 20, which is arranged to cooperate with the operating mechanism of the indicator and also with the switch mechanism which will be considered presently. This rocker shaft is provided at its upper and lower ends with stops 21 and 22 respectively. These stops are adjustably mounted on the rocker shaft 2O and are adapted to'be engaged-by the indicator 19.

The safety switch is placed in the circuit of a no voltage release coil and its mechanism, which is arranged to control the main switch of the hoist, is located in the upper part of the indicator column and is inclosed by aAcap 23. This cap has a lower portion 23EL which is secured to the main shell of the column by a set screw 24, and also an upper portion 25 which fits over and is supported by the lower portion 23a.

Secured to the upper end of the rocker shaft 20 is a lever 26 which is provided with a pin 27 engaged by the pawl 28 which is secured to another lever 29 pivoted to the lower part of the cap 23 at the point 30. The first mentioned lever 26 is provided with another pin 31 to which is connected a spring 32 the other end of which engages a pin 33 near one end of the pawl 23. A link 34 pivotally mounted upon the lever 29, so as to form a toggle therewith, is provided with a small rod 35 which passes through a slotted po-rtion 36 of a supporting insulating plate 37 and engages another lever 38. This lever 38 is pivotally mounted upon a block 39 at the point 43, theblock forming` a support to which a movable contact 40 of the switch is secured. The .block 39 is provided with a pin 41 to which is secured a spring 42 the other end of which engages the rod 35. The Alever 38 is provided with a projection 44 which is adapted to engage a pawl 45 which normally is in engagement with a notched member 46 secured to one side of the block 39. The pawl 45 is held in the notched member 46 by a spring 48. One of the springs 42, in its normal position, lies in a line which lies on one side of the pivotal point 43. In

this position the switch is biased toa closed position. When the rod 35 is moved in the slot 36 until the points 35, 43, and 41 are in l the same straight line the snap mechanism is farther -in the same direction the line in which the spring lies will be on the other side of the pivotal point 43 and the switch will be biased to open position.

vThe leading-in lead 49 comes in through the part 23a ofthe cap 23 and is secured to the stationary contact 47 by a screw 49a. The leading-out lead 50 is connected to a binding post 50a, to which is connected also a conductor 60'., This conductor 60 is connected to a caibon arcing tip 61 which is adapted to break contact with stationary contact last when the switch is opened and to engage said contact first when the switch is closed.

The operation of the switch is as' follows: When the indicator 19 has traveled to its upper or lower limit, it engages one of the stops 21 or 22 which are mounted on the rocker shaft 20. For example let us say:

en the load has reached its upper limit and the indicator 19 engages the stop 21 on the rocker shaft, this stop and shaft are caused to rotate and the` lever 26 mounted von the upper part of the rocker shaft is also rotated forcing the pawl 28 in a direction to stretch the spring 32 and to force back the lever 29 to which the pawl 28 is connected. `The link 34, which isV connected to the leverl 29, is moved with the lever 29 and causes the rod 35 to move from one eXtreme position in the slot 36 toward the other extreme position. When the rod 35 and the lever 38 are moved beyond the critical point the switch is biased to open position, and when the lever 38 has reached the point where the switch is biased to open position with the greatest force the projection 44 of the lever 38 engages the 4pawl 45, throwing it out of engagement with the notched member 46. At this instant the movable contact member 40 is snapped out of engagement with the stationary 'contact member 47 of the switch by the action of the spring 42. Upon the opening of this safety switch the main switch of the hoistis opened and operation of the hoist mechanism is stopped immediately. In order to close the switch again, it is necessary for the pawl 28 to be forced backward to a point where its projection 52 engages an extending portion 53v of the indicator cap 23. It is readily seen that when the projection 52 engages the projecting portion 53 that the pawl 28 will be forced out of engagement with the pin 27 on the lever 26, and due to the tension stored in the spring 32, the link 34 and its rod connections with the lever 38 will be thrown back in their normal positions thus closing the safety switch. In this position the safety switch will again be biased to closed position by the action of spring 42, and the switch will be locked in this position'by the I spring pressed pawl 45. in a critical position. .If the rod 35 is moved Ordinarily upon the opening of the switch, the lever 29 will not be swung backwardfar enough to allow its projection 52 to 'engage the projection 53to throw the pawl 28 out of engagement with the pin 27 so that the switch may be snapped back into closed position. So in order to reset the switch in closed position a handle 55 has been provided which is secured to the rocker shaft 20. This handle is shown in Fig. 3 and is located at the lower extremity of the indicator column 10. This safety snap switch may be operated equally as well when the load has reached a lower limit and the indicator comes into vengagement with l the lower stop 22 on the rocker shaft 20. The stops 21 and 22 are adjustably mounted on'the rocker shaft so that the switch can be opened at any desirable point. j v

The indicator is soconnected to the drum shafts of -hoists 'that the indicator moves a certain distance which is in proportion to the actual distance traveled by the load being raised or lowered the hoist, l.Indi` 13p cator columns of airT length may be used depending upon the proportional -move' inents desired between the actual distance traveled by the load and the'distance traveled by the indicator.

This safety switch arrangement is very Aeffective in controlling the operation of which do not involve a departure from the' spirit and scope of my invention.

What I claim as new is:

l. In electric hoists and similar mechanisms, a safety switch normally biased to closed position, means for locking said switch in closed position, an actuating shaft, a device movable in response to movement of said hoist and cooperating with said actuating shaft at a plurality of points in its travel to operate the same, said shaft when operated by said device causing the opening of said switch.

2. In electric b oists and similar mechanisms, a safety switch normally biased to closed position, locking means for retaining said switch in a4 closed position, a rocker shaft actuated by the operation of said hoist,a system of levers cooperating with said rocker shaft and said switch, one of said levers for biasing the switch to open position, and releasing the locking means to permit said switch to open with a snap action.

3. In electric hoists and similar mecha` nisms, a. safety switch normally biased to closed position, locking means for retaining said switch in a closed position, a rocker shaft actuated by the operation of said hoist, a system of levers coperating with said rocker shaft and said switch, one of said levers for biasingthe switch to open position, releasing the locking means to permit said switch to open with a snap action, and means cooperating with said .rocker shaft for resetting said switch.

4. In electric hoists and similar mechanisms, a safety switch, a rocker shaft actuated by the operation of said hoist, a plurality 'of levers cooperating with the rocker shaft 'and said switch, and a plurality of resilient members alternately biasing the switch to closed and open positions.

5. In electric hoists and similar mechauisms, an indicator column, a threaded shaft therein, an indicator mounted movably ive cents eacnhy addressing 'Washingtomt'tf thereon, a rocker shaft adapted to be actuated by said indicator when the latter is at any one of a plurality of oints, a safety4 switch, means for normal'y locking the switch in closed osition, and means coperating with sai 1 rocker shaft and said` switch to openA said switch at predetermined points. j p y 6. In electric hoists'and similar mechanisms, a rocker shaft, connections between said hoist androcler shaft for giving the latter motionl atpredetermined points, a switch, means for locking the switch in closed position, -spring pressed members coperating j with said rocker shaft and switch for opening-said'switch at said predetermined points, and means active on continued movement of said shaft in the same direction for resetting said switch.

7. In asa'fety device for hoists and. the

`lilre, a switch, resilient means for moving said switch with a sna action into either of two pos1tions,ameans or causing sa1d.resillent means to actuate the switch compnsing fa rocker shaft and afplurality of levers operatively; 'connected tlfiereto and to the switch.

S. In apparatus for controlling electric hoists and similar mechanism, a safety switch, means .for locking said switch in its..

closed position, andrneans comprising a toggle for disengaging said 'locking means and operating the'switch, said means actuyable by the operation of the hoist..

9.*In apparatus for electric hoists and similar'mechanism, a switch, and actuating mechanism therefor, said actuating mechanism whenoperated in one direction ,actuating said switch to open position, and on continued operation in the same direction actuating said switch to closed position, the movementof the hoist beyond a predetermined point causing the operation of the switch to open position.

l0. In a limit switch, a contact making device, and operating means therefor comprising means actuated against a normal bias to move said contact making device to. one position, continued movement of said actuating means in the same direction rendcringsaid bias effective to move said contact making device to original position,

Milwaukee, Wisconsin, June 2, 1910. In testimony whereof I adir; my signature. in the presence of Atwo witnesses.

HERBERT WV. CHENEY.

Witnesses: ,y

Cin-is. n..Braorn' @Lana E. Barman.: y

the .v Qcmxnssioner of Patents, 

